Engine output torque control for powertrain with engageable positive clutches

ABSTRACT

A powertrain system (10) control system/method for controlling engine (12) output torque as a function of sensed degree of engagement of jaw clutch members (62, 64) associated with the engaged ratio of a transmission (14).

BACKGROUND OF THE INVENTION

Related Applications

This application is related to U.S. Ser. No. 09/100,711, filed Jun. 19,1998 and titled START-FROM-STOP ENGINE TORQUE LIMITING, and U.S. Ser.No. 09/314,515 filed May 17, 1999 and titled POWERTRAIN TORQUE CONTROL,both assigned to EATON CORPORATION, assignee of this application.

Field of the Invention

The present invention relates to a control for a vehicular powertraincomprising a fuel-controlled engine and a multiple-ratio drivetrain,including a multiple-speed mechanical transmission and a single- ormultiple-speed drive axle assembly. In particular, the present inventionrelates to a powertrain control wherein the maximum output torque of theengine is limited as a function of the degree of engagement of monitoredjaw clutches.

Description of the Prior Art

Vehicular drivetrains including multiple-speed mechanical transmissions,usually compound transmissions, or simple transmissions coupled withmultiple-speed axles, having 7, 9, 10, 13, 16, 18 or more forward speedratios, are well known in the prior art, especially for heavy-dutyvehicles, as may be seen by reference to U.S. Pat. Nos. 5,370,013;5,527,237 and 4,754,665, the disclosures of which are incorporatedherein by reference. Both synchronized and non-synchronized jaw clutchesare known in the prior art, as may be seen by reference to U.S. Pat.Nos. 5,546,823; 5,588,516 and 5,642,643, the disclosures of which areincorporated herein by reference.

Control systems and methods for calculating engine output torque (alsocalled "flywheel torque") are known in the prior art, as may be seen byreference to U.S. Pat. No. 5,509,867, the disclosure of which isincorporated herein by reference.

Automated and manual transmission systems wherein engine output torqueis controlled and/or limited as a function of engaged gear ratio and/orvehicle speed are known in the prior art, as may be seen by reference toU.S. Pat. Nos. 5,477,827; 5,797,110; 5,457,633; 4,889,014; 5,738,606;5,679,096 and 5,876,302, the disclosures of which are incorporatedherein by reference. As is known, modern vehicular powertrains usuallyinclude electronically controlled engines, which may be controlled as toengine speed and/or engine torque. By way of example, according to theSAE J-1939 data link protocol, commands may be issued to the engine forfueling of the engine in accordance with (a) driver's fuel demand, (b) arequested engine speed, (c) a requested engine torque and/or (d) arequested maximum engine torque and/or engine speed.

While the prior art systems are effective in protecting the vehicledriveline from undue wear and/or damage resulting fromgreater-than-desirable torque being applied for a particular engagedratio and/or driveline configuration, the systems do not preventpossible undue wear and/or damage resulting from partial jaw clutchengagement.

SUMMARY OF THE INVENTION

In accordance with the present invention, an improved controlsystem/method for a vehicular powertrain is provided, which will tend tomaximize vehicle performance while protecting the drivetrain frompossible damage and/or undue wear caused by allowing excessive torque tobe applied thereto under certain vehicle operating conditions, includingpartial jaw clutch engagement. The foregoing is accomplished by limitingpossible engine output torque to a maximum value (torque limit) as afunction of drivetrain ratio and/or vehicle speed. The actual outputtorque of the engine will be some percentage (from 0% to 100%) of thetorque limit determined by the sensed degree of clutch engagement. Byway of example, if full clutch engagement is sensed, the percentage willequal 100%, while at sensed minimal engagement, the percentage may equal20% or less.

Accordingly, it is an object of the present invention to provide a newand improved engine output torque control for a vehicular drivetrainsystem, including a mechanical transmission wherein engine output torqueis controlled as a function of sensed degree of jaw clutch engagement.

This and other objects and advantages of the present invention willbecome apparent from a reading of the description of the preferredembodiment taken in connection with the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of a vehicular powertrain systemincluding an automated mechanical transmission system.

FIGS. 2A, 2B and 2C are schematic illustrations of, respectively,minimal, half and full degrees of jaw clutch engagement.

FIG. 3 is a flow chart representation of the control of the presentinvention.

FIG. 4 is a flow chart representation of the control of an alternateembodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

A vehicular powertrain system 10 of the type advantageously utilizingthe control of the present invention may be seen by reference to FIG. 1.For purposes of illustration, system 10 is an automated mechanicaltransmission system including a fuel-controlled internal combustionengine 12 (such as a well-known diesel engine or the like), amultiple-speed mechanical transmission 14, and a non-positive coupling16 for drivingly coupling the engine 12 to the transmission 14.Typically, non-positive coupling 16 will be a torque converter or afriction master clutch. The transmission 14 further includes an outputshaft 20 for driving the vehicle drive axles 22. The drive axles may beof the single-speed or mulitple-speed type.

Transmission 14 may be of the known mechanical type utilizing positivejaw clutches to engage and disengage selected gears to shafts forchanging the ratio of input shaft rotational speed (IS) to output shaftrotational speed (OS). Transmissions of this type may be seen byreference to U.S. Pat. Nos. 4,764,665; 5,385,056; 5,390,561 and5,416,698.

System 10 may include a plurality of sensors for providing input signals24 to a microprocessor-based control unit 26, which will process theinput signals according to logic rules to generate command outputsignals 28 to various system actuators.

Speed sensors 30, 32 and 34 may be provided to provide input signals tothe controller indicative of engine speed (ES), transmission input shaftspeed (IS), and transmission output shaft speed (OS), respectively. Asensor 36 may be provided to provide an input signal indicative of theoperator setting of the throttle pedal. A driver control console 38 isprovided to allow the operator to select a transmission mode and toprovide an input signal, GR, indicative thereof to the controller 26.

An engine controller 40, preferably microprocessor-based, may beprovided for controlling fueling of the engine and for providinginformation to a data link, DL, indicative of the operating parametersof the engine. Preferably, the data link will comply with a knownprotocol, such as SAE J-1939 or the like. An actuator 42 may be providedfor operating the non-positive coupling 16. A transmission actuator 44may be provided for operating the transmission 14 and for providingsignals indicative of the engaged gear ratio and/or other transmissionoperating parameters. Engaged ratio also may be calculated by comparingthe rotational speeds of the input and output shafts.

The actuator 44 will include position sensors 44A that will provideinformation as to axial position of the shift rail or shift shaft 44Band associated shift fork(s) 44C used to axially position the jawclutches for engaging and disengaging selected ratios (see FIG. 2C).Various types of position sensors, such as (by way of example but notlimitation) mechanical detents, Hall effect switches and the like, maybe utilized within the scope of the present invention and an example ofsuch mechanisms may be seen by reference to U.S. Pat. Nos. 5,729,110 and5,743,143, the disclosures of which are incorporated herein byreference. Axial position sensing may include logic for detectingdeflection-type errors, as seen in U.S. Pat. No. 5,566,070.

As used in this application, and as commonly used in the vehicularindustry, the term "powertrain" will refer to the engine 12, coupling16, transmission 14 and drive axles 12, while the term "drivetrain" willrefer to the coupling 16, the transmission 14 and the axles 22.

Transmission 14 is illustrated as an 18-forward-speed transmissionhaving a direct drive (1:1.00) ratio and two overdrive ratios (see FIG.2B). As is well known, in the direct drive ratio, the shafts aredirectly coupled and torque is not applied to the gears; accordingly, amuch higher torque may be applied to the transmission in direct drivewithout damaging or causing excessive wear to the gears. It also isknown that the higher rotational speeds associated with overdrive (i.e.,ratios wherein output shaft rotational speed exceeds input shaftrotational speed) allows a higher input torque to be applied to thetransmission than in greater than 1:1.00 reduction ratios withoutrisking damage and/or undue wear.

According to the present invention, possible engine torque ("torquelimit") is limited according to the sensed or expected engaged drivelineratio. By way of example, in a heavy-duty truck having a typical dieselengine, in the start ratios, torque may be limited to no more than 1300foot-pounds, in direct drive, torque may be limited to 1800 foot-pounds,and in overdrive, torque may be limited to no more than 1600foot-pounds.

According to the present invention, the maximum output torque of theengine is also limited by the sensed degree of engagement of the jawclutch(es).

As may be seen by reference to FIGS. 2A-2C, a jaw clutch 60 includes twojaw clutch members 62 and 64 carrying interengaging teeth 62A and 64A,which may be axially separated to disengage the clutch or moved axiallytogether to engage the clutch. In the schematic illustration, clutchmember 64 is moved axially relative to member 62 by a shift fork 44Cassociated with a shift rail 44B.

In FIG. 2A, the clutch 60 is only slightly engaged (see tip contact at66). In this condition, full torque will cause torque lock, preventingfull engagement and possibly damage to the tips of the clutch teeth.

In FIG. 2B, the degree of clutch engagement is about 50%, and about 50%to 80% of the torque limit may be transmitted without causing damage tothe clutch teeth.

In FIG. 2C, the clutch 60 is fully engaged and there is no need to limitengine output torque as a function of degree of clutch engagement.

The limiting of engine output torque as a function of sensed degree ofclutch engagement may be a percentage of the torque limit, a presetvalue, or some combination thereof. FIG. 3 is a flow chartrepresentation of the control of the present invention.

Alternatively (see FIG. 4), until substantially full engagement (FIG.2C) is sensed, engine output torque may be minimalized to prevent toothchipping and to minimize torque lock.

Although the present invention has been described with a certain degreeof particularity, it is understood that various modifications arepossible without departing from the spirit and scope of the invention ashereinafter claimed.

I claim:
 1. A method for controlling a vehicular powertrain system (10) comprising a fuel-controlled engine (12), an engine controller for controlling fueling of the engine (40), a multiple-speed transmission (14) having two or more ratios engaged and disengaged by positive jaw clutches (60), said jaw clutches including relatively axially movable first (62) and second (64) jaw clutch members carrying interengageable jaw clutch teeth (62A, 64A), said members relatively axially movable from a disengaged position to (a) a low degree of engagement position wherein said clutch teeth are in minimal engagement (FIG. 2A), and (b) a high degree of engagement position wherein said clutch teeth are at substantially maximum engagement (FIG. 2C), and a controller (26) for receiving input signals (24) and processing same according to logic rules to issue command output signals to system actuators including said engine controller, said method comprising the steps of:(i) sensing engaged transmission ratio; (ii) sensing the degree of engagement of a jaw clutch associated with the engaged transmission ratio; and (iii) limiting output torque of said engine as a function of said sensed degree of engagement.
 2. The method of claim 1 wherein said powertrain includes a sensor (44A) for providing a signal indicative of the axial position of an element (44B, 44C) axially movable with at least one of said clutch members (64).
 3. The method of claim 1 wherein said output torque is limited as a function of engaged transmission ratio.
 4. The method of claim 1 wherein engine output torque is limited to a minimal value unless a high degree of clutch engagement is sensed.
 5. The method of claim 3 wherein engine output torque is limited to a minimal value unless a high degree of clutch engagement is sensed.
 6. A system for controlling a vehicular powertrain system (10) comprising a fuel-controlled engine (12), an engine controller for controlling fueling of the engine (40), a multiple-speed transmission (14) having two or more ratios engaged and disengaged by positive jaw clutches (60), said jaw clutches including relatively axially movable first (62) and second (64) jaw clutch members carrying interengageable jaw clutch teeth (62A, 64A), said members relatively axially movable from a disengaged position to (a) a low degree of engagement position wherein said clutch teeth are in minimal engagement (FIG. 2A), and (b) a high degree of engagement position wherein said clutch teeth are at substantially maximum engagement (FIG. 2C), and a controller (26) for receiving input signals (24) and processing same according to logic rules to issue command output signals to system actuators including said engine controller, said logic rules including rules for:(i) sensing engaged transmission ratio; (ii) sensing the degree of engagement of a jaw clutch associated with the engaged transmission ratio; and (iii) limiting output torque of said engine as a function of said sensed degree of engagement.
 7. The system of claim 6 wherein said powertrain includes a sensor (44A) for providing a signal indicative of the axial position of an element (44B, 44C) axially movable with at least one of said clutch members (64).
 8. The system of claim 6 wherein said logic rules include rules for limiting output torque as a function of engaged transmission ratio.
 9. The system of claim 6 wherein engine output torque is limited to a minimal value unless a high degree of clutch engagement is sensed.
 10. The method of claim 8 wherein engine output torque is limited to a minimal value unless a high degree of clutch engagement is sensed. 